The present disclosure relates to liquid developers and image forming methods using liquid developers.
Generally, development methods for visualizing an electrostatic latent image using charged colored particles are largely divided into dry-type development methods and wet-type development methods. Of these, used in the wet-type development method is a liquid developer obtained by dispersing colored particles in a carrier liquid having electrical insulation property. The charged colored particles in the liquid developer move from the surface of the development roller to the surface of the photosensitive drum according to the principle of electrophoresis, and visualize the electrostatic latent image on the surface of the photosensitive drum. The image thus obtained is transferred from the photosensitive drum onto the recording medium. Since the liquid developer has little possibility of causing scattering of colored particles in the air, it is possible to use fine colored particles having an average particle diameter in submicron size. As a result, it is possible to obtain a high-resolution and high-quality image having excellent tones.
Among image forming methods using the wet-type development methods, a thermal fixing method and an optical fixing method are known as methods for fixing onto a recording medium, an image formed with colored particles. The thermal fixing method is a method for fixing toner onto the recording medium by thermally melting the binder resin, in the case of using the toner in which the colored particles are obtained by dispersing a pigment in the binder resin. The optical fixing method is a method for fixing toner onto the recording medium by using a binder resin having a photoreactive functional group as the binder resin and polymerizing the binder resin by light, in the case of using the toner in which the colored particles are obtained by dispersing a pigment in the binder resin.
However, the thermal fixing method and the optical fixing method require a large amount of thermal energy or light energy for fixing the colored particles onto the recording medium. Thus, in order to reduce the energy consumption in the wet-type development method, there suggested is a liquid developer that includes: a carrier liquid having electrical insulation property, colored particles dispersed in the carrier liquid, and an organic high molecular compound for fixing the colored particles onto the recording medium. This liquid developer characteristically shows that an organic high molecular compound is dissolved in the carrier liquid, and the pigment is used for the colored particles.